DOCSLIB.ORG

Open Ocean Dead-Zones in the Tropical J I Northeast Atlantic

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Open Ocean Dead-Zones in the Tropical J I Northeast Atlantic Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Biogeosciences Discuss., 11, 17391–17411, 2014 www.biogeosciences-discuss.net/11/17391/2014/ doi:10.5194/bgd-11-17391-2014 BGD © Author(s) 2014. CC Attribution 3.0 License. 11, 17391–17411, 2014 This discussion paper is/has been under review for the journal Biogeosciences (BG). Open ocean Please refer to the corresponding final paper in BG if available. dead-zones Open ocean dead-zone in the tropical J. Karstensen et al. North Atlantic Ocean Title Page 1 1 1 1 1 2 J. Karstensen , B. Fiedler , F. Schütte , P. Brandt , A. Körtzinger , G. Fischer , Abstract Introduction R. Zantopp1, J. Hahn1, M. Visbeck1, and D. Wallace3 Conclusions References 1GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany Tables Figures 2Faculty of Geosciences and MARUM, University of Bremen, Bremen, Germany 3Halifax Marine Research Institute (HMRI), Halifax, Canada J I Received: 3 November 2014 – Accepted: 13 November 2014 – Published: 12 December 2014 J I Correspondence to: J. Karstensen ([email protected]) Back Close Published by Copernicus Publications on behalf of the European Geosciences Union. Full Screen / Esc Printer-friendly Version Interactive Discussion 17391 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract BGD The intermittent appearances of low oxygen environments are a particular thread for marine ecosystems. Here we present first observations of unexpected low (< 11, 17391–17411, 2014 2 µmolkg−1) oxygen environments in the open waters of the eastern tropical North −1 5 Atlantic, a region where typically oxygen concentration does not fall below 40 µmolkg . Open ocean The low oxygen zones are created just below the mixed-layer, in the euphotic zone of dead-zones high productive cyclonic and anticyclonic-modewater eddies. A dynamic boundary is created from the large swirl-velocity against the weak background flow. Hydrographic J. Karstensen et al. properties within the eddies are kept constant over periods of several months, while net 10 respiration is elevated by a factor of 3 to 5 reducing the oxygen content. We repeatedly observed low oxygen eddies in the region. The direct impact on the ecosystem is Title Page evident from anomalous backscatter behaviour. Satellite derived global eddy statistics Abstract Introduction do not allow to estimate the large-scale impact of the eddies because their vertical structure (mixed-layer depth, euphotic depth) play a key role in creating the low oxygen Conclusions References 15 environment. Tables Figures 1 Introduction J I J I The concentration of dissolved oxygen (DO) in seawater is of critical importance to almost all marine life and oceanic biogeochemical cycling (Wilding, 1939; Diaz and Back Close Rosenberg, 2008; Vaquer-Sunyer and Duarte, 2008; Wright et al., 2012; Kalvelage Full Screen / Esc 20 et al., 2011). Local DO concentrations are the result of a delicate balance between oxygen supply and consumption and eventually regions of extreme low oxygen Printer-friendly Version content are created: at the microscale at particle boundaries (Alldredge and Cohen, 1987), at the mesoscale as coastal dead-zones (Diaz and Rosenberg, 2008) or at Interactive Discussion the large scale such as eastern boundary Oxygen Minimum Zones (OMZ) (Luyten 25 et al., 1983; Karstensen et al., 2008). Understanding processes that control the 17392 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | DO supply/consumption balance, and any possible alterations over time, remain a challenge of current research. BGD Critical DO concentration thresholds have been identified, which lead to major 11, 17391–17411, 2014 reorganizations of the marine ecosystems (Vaquer-Sunyer and Duarte, 2008; Wright 5 et al., 2012; Kalvelage et al., 2011). For higher trophic levels, such as fish, the impact of a certain DO levels on metabolism and as such fitness, is species dependent Open ocean (Wilding, 1939). Nevertheless, for DO below 20 µmolkg−1 (“severe hypoxia”) mass dead-zones mortality of fish has been reported (Diaz and Rosenberg, 2008). Also triggered by severe hypoxia DO levels, microbes begin to convert nitrite and ammonium to nitrogen J. Karstensen et al. 10 gas, and this remove fixed nitrogen from the water which in turn limits primary productivity (Wright et al., 2012; Kalvelage et al., 2011). A next distinct DO threshold Title Page is for concentrations below about 5 µmolkg−1 when microbes begin to utilize nitrate (and other nitrogen species) as terminal electron acceptors in anaerobic respiration Abstract Introduction (“denitrification”) (Wright et al., 2012; Kalvelage et al., 2011). Finally, when DO reach −1 Conclusions References 15 concentrations around 1 µmolkg (“anoxia”), only specifically adapted microbes can exist (Wright et al., 2012). Tables Figures The pelagic zones of the eastern tropical North Atlantic OMZ are considered to −1 be “hypoxic”, with minimal DO of hardly below 40 µmolkg (Stramma et al., 2009; J I Karstensen et al., 2008). As such it is assumed that the DO levels pose on the regional J I 20 ecosystem some limitation in biodiversity primarily through avoidance and maybe an increased mortality (Vaquer-Sunyer and Duarte, 2008). The region is thus very much Back Close in contrast to the major OMZs in the eastern North and South Pacific Ocean and Full Screen / Esc the northern Indian Ocean where DO concentrations pass all DO thresholds outlined above, and as such specifically adapted ecosystems must exists. Printer-friendly Version 25 However, here we report on recent observations of extreme low DO, characterizing severe hypoxia and even anoxia with horizontal scales of about 100 km and vertical Interactive Discussion scales of about 100 m, exists in the eastern tropical North Atlantic. 17393 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 Data and methods BGD 2.1 Moored oxygen sensors 11, 17391–17411, 2014 DO time series were acquired at the Cape Verde Ocean Observatory (CVOO) mooring. CVOO is located in the eastern tropical North Atlantic, about 100 km northeast of the ◦ 0 ◦ 0 Open ocean 5 Cape Verde Island Sao Vicente (17 35 N, 24 15 W) and approximately 800 km from dead-zones the Mauritanian coast (Fig.1). Since 2006 the observatory is equipped with oxygen optodes, while since the beginning of 2008 at least one optode was installed in the J. Karstensen et al. upper 60 m of the water colmn. Oxygen measurements at the CVOO mooring were done with AADI Aanderaa 10 oxygen optodes (type 3830). A calibration was done against CTD/oxygen sensor Title Page (Sea-Bird Electronics 43 Clark electrode) data for the deployment period from 2009 Abstract Introduction to 2014 before and after the deployment phase. For each optode, 17 independent calibration points were obtained, choosing locations with weak vertical oxygen gradient. Conclusions References A lab calibration at zero oxygen concentration was also performed by submerging the Tables Figures 15 optodes into a sodium sulfite solution. All calibration points were used to derive a final calibration equation, while the chemically forced (and thus more precise) zero oxygen J I calibration was weighted three times higher than the CTD/oxygen cast references. The difference between calibration point observations and calibrated optode suggests an J I −1 overall rms error of 3 µmolkg . Comparison of the chemically forced zero oxygen Back Close 20 phase data and the phase readings during the anoxic event suggests a higher accuracy of about 1 µmolkg−1. Pressure and salinity variability was corrected according to the Full Screen / Esc AADI manual. Printer-friendly Version 2.2 Argo float Interactive Discussion Data from a PROVOR Profiling Argo Float (WMO 6900632; Martec Inc., France), 25 equipped with a standard CTD (SBE 41CP; Sea-Bird Electronics, Bellevue, USA), an oxygen optode (3830; Aanderaa Data Instruments, Bergen, Norway) and 17394 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | a transmissometer (CRV5; WETLabs, Philomath, USA) was used. The float was programmed to conduct every 5th day a vertical profile between 400 db and the BGD surface with a vertical resolution of 5 db. Transmitted DO concentrations were corrected 11, 17391–17411, 2014 for salinity effects and a pressure correction of 4 % per 1000 db was applied to 5 the data. After deployment, a ship-borne CTD cast that included measurements for DO (Winkler Titration and a Sea-Bird SBE 43 Clark Electrode), was conducted next Open ocean to the deployment location and used for post offset correction of float-based DO dead-zones measurements. Transmissometer data was obtained in units of m−1 (beam attenuation coefficient) based on the factory calibration. Biofouling within the optical path was J. Karstensen et al. 10 accounted for by subsequently subtracting each profile’s minimum beam attenuation value from the respective profile data. Title Page 2.3 Eddy tracking Abstract Introduction For detecting and tracking eddy-like structures from the daily merged SLA data, an Conclusions References algorithm based on the Okubo–Weiß method was applied. The method is robust and Tables Figures 15 widely used to detect eddies in satellite data as well as on numerical model output (Chelton et al., 2007; Sangrà et al., 2009). Analysing the contribution of relative vorticity J I on the strain tensor, an eddy is defined as a region of negative W (vorticity dominates over strain) surrounded by a region of positive W (strain dominates over vorticity).
Load more

Recommended publications
  • Effects of Eutrophication on Stream Ecosystems
    EFFECTS OF EUTROPHICATION ON STREAM ECOSYSTEMS Lei Zheng, PhD and Michael J. Paul, PhD Tetra Tech, Inc. Abstract This paper describes the effects of nutrient enrichment on the structure and function of stream ecosystems. It starts with the currently well documented direct effects of nutrient enrichment on algal biomass and the resulting impacts on stream chemistry. The paper continues with an explanation of the less well documented indirect ecological effects of nutrient enrichment on stream structure and function, including effects of excess growth on physical habitat, and alterations to aquatic life community structure from the microbial assemblage to fish and mammals. The paper also dicusses effects on the ecosystem level including changes to productivity, respiration, decomposition, carbon and other geochemical cycles. The paper ends by discussing the significance of these direct and indirect effects of nutrient enrichment on designated uses - especially recreational, aquatic life, and drinking water. 2 1. Introduction 1.1 Stream processes Streams are all flowing natural waters, regardless of size. To understand the processes that influence the pattern and character of streams and reduce natural variation of different streams, several stream classification systems (including ecoregional, fluvial geomorphological, and stream order classification) have been adopted by state and national programs. Ecoregional classification is based on geology, soils, geomorphology, dominant land uses, and natural vegetation (Omernik 1987). Fluvial geomorphological classification explains stream and slope processes through the application of physical principles. Rosgen (1994) classified stream channels in the United States into seven major stream types based on morphological characteristics, including entrenchment, gradient, width/depth ratio, and sinuosity in various land forms.
    [Show full text]
  • Microscale Ecology Regulates Particulate Organic Matter Turnover in Model Marine Microbial Communities
    ARTICLE DOI: 10.1038/s41467-018-05159-8 OPEN Microscale ecology regulates particulate organic matter turnover in model marine microbial communities Tim N. Enke1,2, Gabriel E. Leventhal 1, Matthew Metzger1, José T. Saavedra1 & Otto X. Cordero1 The degradation of particulate organic matter in the ocean is a central process in the global carbon cycle, the mode and tempo of which is determined by the bacterial communities that 1234567890():,; assemble on particle surfaces. Here, we find that the capacity of communities to degrade particles is highly dependent on community composition using a collection of marine bacteria cultured from different stages of succession on chitin microparticles. Different particle degrading taxa display characteristic particle half-lives that differ by ~170 h, comparable to the residence time of particles in the ocean’s mixed layer. Particle half-lives are in general longer in multispecies communities, where the growth of obligate cross-feeders hinders the ability of degraders to colonize and consume particles in a dose dependent manner. Our results suggest that the microscale community ecology of bacteria on particle surfaces can impact the rates of carbon turnover in the ocean. 1 Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. 2 Department of Environmental Systems Science, ETH Zurich, Zürich 8092, Switzerland. Correspondence and requests for materials should be addressed to O.X.C. (email: [email protected]) NATURE COMMUNICATIONS | (2018) 9:2743 | DOI: 10.1038/s41467-018-05159-8 | www.nature.com/naturecommunications 1 ARTICLE NATURE COMMUNICATIONS | DOI: 10.1038/s41467-018-05159-8 earning how the composition of ecological communities the North Pacific gyre20.
    [Show full text]
  • Plankton Community Composition, Organic Carbon and Thorium-234 Particle Size Distributions, and Particle Export in the Sargasso Sea
    Journal of Marine Research, 67, 845–868, 2009 Plankton community composition, organic carbon and thorium-234 particle size distributions, and particle export in the Sargasso Sea by H. S. Brew1, S. B. Moran1,2, M. W. Lomas3 and A. B. Burd4 ABSTRACT Measurements of plankton community composition (eight planktonic groups), particle size- fractionated (10, 20, 53, 70, and 100-␮m Nitex screens) distributions of organic carbon (OC) and 234Th, and particle export of OC and 234Th are reported over a seasonal cycle (2006–2007) from the Bermuda Atlantic Time-Series (BATS) site. Results indicate a convergence of the particle size distributions of OC and 234Th during the winter-spring bloom period (January–March, 2007). The observed convergence of these particle size distributions is directly correlated to the depth-integrated abundance of autotrophic pico-eukaryotes (r ϭ 0.97, P Ͻ 0.05) and, to a lesser extent, Synechococcus (r ϭ 0.85, P ϭ 0.14). In addition, there are positive correlations between the sediment trap flux of OC and 234Th at 150 m and the depth-integrated abundance of pico-eukaryotes (r ϭ 0.94, P ϭ 0.06 for OC, and r ϭ 0.98, P Ͻ 0.05 for 234Th) and Synechococcus (r ϭ 0.95, P ϭ 0.05 for OC, and r ϭ 0.94, P ϭ 0.06 for 234Th). An implication of these observations and recent modeling studies (Richardson and Jackson, 2007) is that, although small in size, pico-plankton may influence large particle export from the surface waters of the subtropical Atlantic.
    [Show full text]
  • A View of Physical Mechanisms for Transporting Harmful Algal Blooms to T Massachusetts Bay ⁎ Yu Zhanga, , Changsheng Chenb, Pengfei Xueb,1, Robert C
    Marine Pollution Bulletin 154 (2020) 111048 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul A view of physical mechanisms for transporting harmful algal blooms to T Massachusetts Bay ⁎ Yu Zhanga, , Changsheng Chenb, Pengfei Xueb,1, Robert C. Beardsleyc, Peter J.S. Franksd a College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, PR China b School for Marine Science and Technology, University of Massachusetts-Dartmouth, New Bedford, MA 02744, USA c Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA d Integrative Oceanography Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA ARTICLE INFO ABSTRACT Keywords: Physical dynamics of Harmful Algal Blooms in Massachusetts Bay in May 2005 and 2008 were examined by the Harmful algal bloom simulated results. Reverse particle-tracking experiments suggest that the toxic phytoplankton mainly originated Massachusetts Bay from the Bay of Fundy in 2005 and the western Maine coastal region and its local rivers in 2008. Mechanism Ocean modeling studies suggest that the phytoplankton were advected by the Gulf of Maine Coastal Current (GMCC). In 2005, Lagrangian flow Nor'easters increased the cross-shelf surface elevation gradient over the northwestern shelf. This intensified the Eastern and Western MCC to form a strong along-shelf current from the Bay of Fundy to Massachusetts Bay. In 2008, both Eastern and Western MCC were established with a partial separation around Penobscot Bay before the outbreak of the bloom. The northeastward winds were too weak to cancel or reverse the cross-shelf sea surface gradient, so that the Western MCC carried the algae along the slope into Massachusetts Bay.
    [Show full text]
  • NIST Recommended Practice Guide : Particle Size Characterization
    NATL INST. OF, STAND & TECH r NIST guide PUBLICATIONS AlllOb 222311 ^HHHIHHHBHHHHHHHHBHI ° Particle Size ^ Characterization Ajit Jillavenkatesa Stanley J. Dapkunas Lin-Sien H. Lum Nisr National Institute of Specidl Standards and Technology Publication Technology Administration U.S. Department of Commerce 960 - 1 NIST Recommended Practice Gu Special Publication 960-1 Particle Size Characterization Ajit Jillavenkatesa Stanley J. Dapkunas Lin-Sien H. Lum Materials Science and Engineering Laboratory January 2001 U.S. Department of Commerce Donald L. Evans, Secretary Technology Administration Karen H. Brown, Acting Under Secretary of Commerce for Technology National Institute of Standards and Technology Karen H. Brown, Acting Director Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose. National Institute of Standards and Technology Special Publication 960-1 Natl. Inst. Stand. Technol. Spec. Publ. 960-1 164 pages (January 2001) CODEN: NSPUE2 U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 2001 For sale by the Superintendent of Documents U.S. Government Printing Office Internet: bookstore.gpo.gov Phone: (202)512-1800 Fax: (202)512-2250 Mail: Stop SSOP, Washington, DC 20402-0001 Preface PREFACE Determination of particle size distribution of powders is a critical step in almost all ceramic processing techniques. The consequences of improper size analyses are reflected in poor product quality, high rejection rates and economic losses.
    [Show full text]
  • A Primer on Limnology, Second Edition
    BIOLOGICAL PHYSICAL lake zones formation food webs variability primary producers light chlorophyll density stratification algal succession watersheds consumers and decomposers CHEMICAL general lake chemistry trophic status eutrophication dissolved oxygen nutrients ecoregions biological differences The following overview is taken from LAKE ECOLOGY OVERVIEW (Chapter 1, Horne, A.J. and C.R. Goldman. 1994. Limnology. 2nd edition. McGraw-Hill Co., New York, New York, USA.) Limnology is the study of fresh or saline waters contained within continental boundaries. Limnology and the closely related science of oceanography together cover all aquatic ecosystems. Although many limnologists are freshwater ecologists, physical, chemical, and engineering limnologists all participate in this branch of science. Limnology covers lakes, ponds, reservoirs, streams, rivers, wetlands, and estuaries, while oceanography covers the open sea. Limnology evolved into a distinct science only in the past two centuries, when improvements in microscopes, the invention of the silk plankton net, and improvements in the thermometer combined to show that lakes are complex ecological systems with distinct structures. Today, limnology plays a major role in water use and distribution as well as in wildlife habitat protection. Limnologists work on lake and reservoir management, water pollution control, and stream and river protection, artificial wetland construction, and fish and wildlife enhancement. An important goal of education in limnology is to increase the number of people who, although not full-time limnologists, can understand and apply its general concepts to a broad range of related disciplines. A primary goal of Water on the Web is to use these beautiful aquatic ecosystems to assist in the teaching of core physical, chemical, biological, and mathematical principles, as well as modern computer technology, while also improving our students' general understanding of water - the most fundamental substance necessary for sustaining life on our planet.
    [Show full text]
  • Particle Aggregation During a Diatom Bloom. 11. Biological Aspects
    MARINE ECOLOGY PROGRESS SERIES Published January 24 Mar. Ecol. Prog. Ser. Particle aggregation during a diatom bloom. 11. Biological aspects Ulf Riebesell Alfred Wegener Institute for Polar and Marine Research, Colurnbusstr., D-2850 Bremerhaven. Germany ABSTRACT: For a 6 wk period covering the time before, during, and after the phytoplankton spring bloom, macroscopic aggregates (20.5 mm diameter) were repeatedly collected and water column properties simultaneously measured at a fixed station in the Southern North Sea. Distinct changes in aggregate structure and composition were observed during the study. Predominantly detrital aggregates dur~ngthe early phase of the study were followed by diatom-dominated algal flocs around the peak of the bloom. Mucus-rich aggregates containing both algal and detrital components and with large numbers of attached bacteria dominated the post-bloom interval. The phytoplankton succession within the aggregates closely reflected the succession in the water column with a time delay of a few days. Algal flocculation did not occur as a simultaneous aggregation of the entire phytoplankton community, but as a successional aggregat~onof selected diatom species. Although the concentrations of ~norganicnutrients diminished considerably during the development of the phytoplankton bloom, the termination of the bloom appeared to be mostly controlled by physical coagulation processes. The importance of biologically-controlled factors for physical coagulation is discussed. INTRODUCTION stickiness, proposed that physical processes alone could determine the time and extent of algal aggregation. Mass flocculation during diatom blooms as predicted Based on a physical coagulation model, Jackson pre- by Smetacek (1985) has since been documented both in dicted that the rate of aggregation strongly depends on the field (Kranck & Milligan 1988, Alldredge & Got- algal concentration.
    [Show full text]
  • Eutrophication and Health Printed Infrance- PRINTED ONWHITECHLORINE-FREE PAPER Reproduction Isauthorised Providedthesourceisacknowledged
    World Health Organization EUROPEAN COMMISSION Regional Office for Europe Eutrophication and health 40 water Eutrophication and health Algal blooms, “red tides”, “green tides”, fish kills, inedible shellfish, blue algae and public health threats. What is the common link ? The answer is, EUTROPHICATION: a complex process which occurs both in fresh and marine waters, where excessive development of certain types of algae disturbs the aquatic ecosystems and becomes a threat for animal and human health. The primary cause of eutrophication is an excessive concentration of plant nutrients originating from agriculture or sewage treatment. The purpose of this booklet is to describe in a simple way the causes of eutrophication, the environmental effects, the associated nuisances and health risk as well as the preventive and mitigating measures. It is hoped that the booklet, which represents a collaborative effort between the European Commission and the WHO, will contribute to a better understanding of the problem of eutrophication and a more effective control of nutrient enrichment in our lakes, rivers ans seas. preface Dr Günter KLEIN Prudencio PERERA Head of office Director WHO European Centre for Environment Environment Quality and Natural Resources and Health Bonn Office European Commission A great deal of additional information on the European Union is available on the Internet. It can be accessed through the Europa server (http://europa.eu.int). Cataloguing data can be found at the end of this publication. Luxembourg: Office for Official Publications of the European Communities, 2002 ISBN 92-894-4413-4 © European Communities, 2002 Reproduction is authorised provided the source is acknowledged. Printed in France - PRINTED ON WHITE CHLORINE-FREE PAPER Local authorities - this publication is meant for you WHO’s Regional Office for Europe is regularly approached to provide technical or practical advice on a large number of questions related to health and the environment.
    [Show full text]
  • Environmental Studies Program: Ongoing Study
    Environmental Studies Program: Ongoing Study Title Assessing the Impact of Oil Spills Using Three-Dimensional Oil Spill Modeling (NSL #PC-16-03) Administered by Pacific OCS Region BOEM Contact(s) Susan Zaleski ([email protected]) Procurement Type(s) Inter-agency Agreement Conducting Organizations(s) National Oceanic and Atmospheric Administration, Office of Response and Restoration Total BOEM Cost $478,000 Performance Period FY 2016–2022 Final Report Due July 21, 2022 Date Revised January 22, 2021 PICOC Summary Problem BOEM has limited ability to assess the impact of a potential oil spill to subsurface biota. Intervention Pilot test a 3D oil spill model and expand BOEM Pacific Region’s oil spill modeling capability. Comparison Compare new model outputs to previous analyses. Outcome Updated oil spill modeling capability Context Southern California Planning Area BOEM Information Need(s): Currently the offshore oil and gas risk analysis conducted by the BOEM Pacific Region is based on a two-dimensional oil spill model, which only predicts surface transport of oil spills. However, oil spills can have significant impact to the subsurface. The impact of oil spills to the subsurface can only be predicted using three-dimensional oil spill modeling. The aim of this study is to implement a three-dimensional oil spill model in southern California and to assess the impact of oil spills to subsurface biota. This study will expand BOEM Pacific Region’s capability to conduct oil spill risk analysis in southern California. Background: BOEM Pacific region currently uses the General NOAA Oil Modeling Environment (GNOME), which is a two-dimensional oil spill model, for oil and gas risk analysis.
    [Show full text]
  • Environmental and Biological Consequences of Microplastic Within Marine Habitats
    ENVIRONMENTAL AND BIOLOGICAL CONSEQUENCES OF MICROPLASTIC WITHIN MARINE HABITATS by MARK ANTHONY BROWNE A thesis submitted to the University of Plymouth in partial fulfilment for the degree of DOCTOR OF PHILOSOPHY School of Biological Sciences October 2007 Frontispiece. Plastic debris on a beach in Looe, Cornwall, UK. Copyright Statement This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and that no quotation from the thesis and no information derived fr om it may be published without the author's prior consent. f:D . Item No loo Sl0 8ýka b ý..ý ý'rZwrk "(klýSlS363,73441301" Mark Anthony Browne October 2007 ii Environmental and biological consequences of microscopic plastic within marine habitats Mark Anthony Browne Abstract Large pieces of plastic greater than a millimetre in diameter contaminate marine habitats worldwide and the associated environmental problems are well documented. In addition tiny fragments of plastic debris less than a millimetre in size have recently been reported. This thesis examines the distribution and environmental consequences of microscopic particles of plastic within marine habitats. To quantify the relative influence of wind and depositional environment on the accumulation of plastic debris, a mensurative experiment was conducted in a macrotidal Estuary. The overall trend was that material accumulated in down-wind sites. However, the relative importance of wind as a transport agent depended on the size and density of the plastic. Natural sediments are transported according to their size; but the extent to which models of sediment dynamics could be applied to the transport of plastic debris remains untested.
    [Show full text]
  • A Dual-Tracer Approach to Estimate Upwelling Velocity in Coastal Southern California ∗ William Z
    Earth and Planetary Science Letters 422 (2015) 138–149 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl A dual-tracer approach to estimate upwelling velocity in coastal Southern California ∗ William Z. Haskell II , Douglas E. Hammond, Maria G. Prokopenko Earth Sciences Dept., University of Southern California, Los Angeles, CA 90089, USA a r t i c l e i n f o a b s t r a c t 7 Article history: The distribution of the cosmogenic radionuclide Be (t1/2 = 53d) in the surface ocean has previously been Received 19 December 2014 used to estimate upwelling velocity in the open ocean. However, the loss of 7Be to particle export has Received in revised form 18 March 2015 limited this approach in high particle density environments like the continental margins. In this study, we Accepted 9 April 2015 combine a mass balance of 7Be with a 234Th budget in the surface ocean to constrain the loss of 7Be to Available online 28 April 2015 particle sinking at the San Pedro Ocean Time-series (SPOT) in the inner Southern California Bight during Editor: J. Lynch-Stieglitz −1 7 spring 2013. Upwelling velocities (all in md ) determined from the Be mass balance were observed to Keywords: increase from 0.5 ± 0.6in January to 2.5 ± 1.3in May, then decrease to 1.2 ± 0.5in June. These results upwelling agree within uncertainty with upwelling velocities derived from the monthly Bakun Upwelling Index, −1 particle export which ranged from 0.1 to 2.8 m d , supporting the pressure-field-based approach.
    [Show full text]
  • Early Diverging Lineages Within Cryptomycota and Chytridiomycota Dominate the Fungal Communities in Ice-Covered Lakes of the Mcmurdo Dry Valleys, Antarctica
    See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/320986652 Early diverging lineages within Cryptomycota and Chytridiomycota dominate the fungal communities in ice-covered lakes of the McMurdo Dry Valleys, Antarctica Article in Scientific Reports · November 2017 DOI: 10.1038/s41598-017-15598-w CITATIONS READS 2 144 6 authors, including: Keilor Rojas- Jimenez Christian Wurzbacher University of Costa Rica Technische Universität München 28 PUBLICATIONS 289 CITATIONS 59 PUBLICATIONS 398 CITATIONS SEE PROFILE SEE PROFILE Elizabeth Bourne Amy Chiuchiolo Leibniz-Institute of Freshwater Ecology and Inland Fisheries Montana State University 9 PUBLICATIONS 450 CITATIONS 11 PUBLICATIONS 322 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: MANTEL View project HGT in aquatic ecosystems View project All content following this page was uploaded by Keilor Rojas-Jimenez on 10 November 2017. The user has requested enhancement of the downloaded file. www.nature.com/scientificreports OPEN Early diverging lineages within Cryptomycota and Chytridiomycota dominate the fungal communities Received: 25 August 2017 Accepted: 30 October 2017 in ice-covered lakes of the McMurdo Published: xx xx xxxx Dry Valleys, Antarctica Keilor Rojas-Jimenez 1,2, Christian Wurzbacher1,3, Elizabeth Charlotte Bourne3,4, Amy Chiuchiolo5, John C. Priscu5 & Hans-Peter Grossart 1,6 Antarctic ice-covered lakes are exceptional sites for studying the ecology of aquatic fungi under conditions of minimal human disturbance. In this study, we explored the diversity and community composition of fungi in fve permanently covered lake basins located in the Taylor and Miers Valleys of Antarctica.
    [Show full text]